This section provides background information related to the present disclosure which is not necessarily prior art.
Various vehicle driveline components, such as transfer cases, power take-off units and axle assemblies, can include a two-speed transmission having a transmission shaft or element that can be moved between two positions to cause the transmission to operate in two discrete speed or gear reductions ratios. A clutch or shift fork is often times employed to translate the transmission element along an axis between the two positions. The shift fork can be translated by any type of linear motor, such as a solenoid plunger, a hydraulic or pneumatic cylinder, or a follower that engages a rotary cam.
It is known in the art to provide a compliance spring in a force transmission path between the linear motor and the shift fork. In the event that movement of the transmission element along the axis in a first direction from a first position to a second position is blocked, for example when mating teeth on another element of the transmission are disposed in the path of teeth on the transmission element, the compliance spring permits the linear motor to be operated without causing corresponding axial motion of the shift fork. In this regard, the linear motor can be operated to store energy in the compliance spring. The energy stored in the compliance spring can be released to move the shift fork when movement of the transmission element is no longer blocked.
It is also known in the art to provide a return spring, which may or may not be used in conjunction with a compliance spring. The return spring is typically located between an output of the linear motor and the shift fork and is employed to bias the shift fork toward the output of the linear motor. The biasing of the shift fork correspondingly biases the transmission element along the axis in a second direction that is opposite the first direction.
One drawback associated with the known arrangements that employ a compliance spring and/or a biasing spring concerns a situation in which the transmission element becomes unresponsive to the output of the linear motor. This can happen, for example, if the shift fork were to break or to wear to the point where it is no longer connected to the hub. In such cases, the compliance spring and the biasing spring would have no effect on the positioning of the movable transmission element.